2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/198098Recent theoretical and observational motivations for existence of a decaying Ultra Heavy Dark Matter (UHDM) are reviewed. We show that present data from Ultra High Energy Cosmic Rays (UHECRs) and SN - Ia are compatible with a relatively short lifetime of UHDM.Invited talk; To apppear in Proceedings of "Cosmion99", Moscow, 17-24 Oct.1999 A typo corrected; one reference addedAstrophysicstext